Figure 2-10.--Type JA switch.

bridges two adjacent contacts simultaneously (for

smaller than the J switch. This feature saves

example, contacts 1 and 2 when the switch is

switchboard space. This feature also makes

operated), the blade breaks contact 1 before making

disassembly a lot easier. Remember, however, that a

the next alternate contact 3 (for example, in the 2JR

faulty switch should be repaired only when immediate

replacement is not possible, and it should be replaced

switch, alternate terminals may be connected to an

independent source of ac power without danger of

at the earliest opportunity. The JR switch is divided

into four types: 1JR, 2JR, 3JR, and 4JR.

short circuit during movement of the switch blade).

Barriers are also provided between sections to

The 1JR switch has only one movable contact per

prevent terminals from turning and shorting to

section. This movable contact bridges two adjacent

adjacent terminals.

stationary contacts.

If the sections are not uniform, the switch will be

The 2JR switch has two movable contacts per

designated by JRSP followed by the number of

section, 180 apart. Each movable contact bridges two

sections.

adjacent stationary contacts.

The JR switch has a stop deck, which permits

The 3JR switch uses one of the stationary contacts

setting the switch to the number of positions desired.

as a common terminal. This stationary contact is

Pins or screws inserted in the stop deck immediately

connected, in turn, to each of the other stationary

after the desired last position will limit the switch

contacts of the section by a single-wiper contact. The

movement to the positions between these points.

3JR switch is used for selecting one of several (up to

TYPE JL.-- The JL switch is identical to the JR,

seven) inputs.

except in size, mounting facility, and electrical rating.

The diameter of the JL deck is approximately 1 3/4

The 4JR switch is designed as an either or both

inches, whereas the diameter of the JR deck is

switch with two movable contacts per section. Each

approximately 2 1/4 inches. The rating of the JL

movable contact bridges three adjacent stationary

switch is 120 volts, 60 Hz, 5 amperes. Standard types

contacts. This switch is used to select either or both of

are available in three, five, and ten sections. The JL

two indicators or synchros. The positions for

switch has a threaded bushing for single-hole

energizing two indicators are as follows:

mounting.

90 right--both indicators energized.

TYPE JA.-- The JA switch (fig. 2-10) was devel-

45 right--indicator 1 energized only.

oped primarily for circuit selection in sound-powered

0--off.

telephone applications. It provides a greater number of

selections and is a smaller switch than the JR switch.

45 left--indicator 2 energized only.

The JA switch is furnished only with common rotor

When the 4JR switch is in the OFF position, both

sections (as shown in fig. 2-11). Sixteen-position and

indicators are connected together, but they are

30-position JA switches permit selection of 16 and 30

disconnected from the power supply.

circuits, respectively. With the JR switch, the maximum

number of possible selections is seven.

The designations of JR switches are determined

by the type of section (rotary and stationary contacts)

The JA switch also provides lower contact

followed by the number of sections in the switch. For

resistance by using either silver or silver-overlay

example, a 2JR10 switch denotes a JR switch with ten

contacts. With brass or copper, an insulating film

2JR sections.

The JR switch is stocked in multiples of five

sections (up to 25 sections). In some cases, a switch

with a number of sections (not a multiple of five) has

been installed. If this switch must be replaced, a switch

with the next largest number of sections that is a

multiple of five should be installed, if space permits.

Type JR switches are rated at 120 volts, 60 Hz, 10

amperes. The switch should not be used on dc circuits

because of the possibility of severely burned contacts

when the switch is operated slowly (teased). The

switch is the nonshorting type. Although the blade

Figure 2-10.--Type JA switch.

2-6